Piercing apparatus

ABSTRACT

A piercing apparatus including a housing provided with a bore accommodating a punch support slidable axially in the bore. A thrust element is slidable axially in the punch support, the punch support being adapted to receive an axially slidable piercing punch and the thrust element being arranged and adapted to be non-rotatably engaged with and to exert a piercing thrust on a punch received in the punch support. Locating means prevent rotation of the thrust element relative to the support and rotation of the support relative to the housing. At least one said locating means comprises a resiliently-loaded guide element engaging an axially extending groove.

O Unlted States Patent [191 [111 3,772,954 De Ruwe et al. Nov. 20, 1973 [54] PIERCING APPARATUS 3,205,742 9/1965 Williamson 83/698 X l h 0d C l' D R [76] nventors 3 1 22; xf s t Primary ExaminerAndrew R. Juhasz Leonardus Honlngs, Hoofdstraat 54, j r f a Bray Mierlo-Hout, both of Netherlands nomey" aters et [22] Filed: July 28, 1972 [21] App]. No.: 276,264 A piercing apparatus including a housing provided with a bore accommodating a punch support slidable [52] us CL 835 83/104 83/563 axially in the bore. A thrust element is slidable axially 5 83/635 83/698 in the punch support, the punch support being [51] Int Cl B26d 5/08 adapted to receive an axially slidable piercing punch [58] Fieid 563 582 and the thrust element being arranged and adapted to be non-rotatably engaged with and to exert a piercing thrust on a punch received in the punch support. Lo- [56] Reerences Cited eating means prevent rotation of the thrust element relative to the support and rotation of the support rel UNITED STTES PATENTS ative to the housing. At least one said locating means Wetsbeck et X comprises a resiliently loaded guide element engaging glrnazlzgn an axially extending g 3,114,280 12/1963 Schott 83/698 X 16 Claims, 4 Drawing Figures PIERCING APPARATUS BACKGROUND OF THE INVENTION The present invention relates to piercing apparatus, comprising a housing with a bore accommodating a punch support, slidable axially in said bore and having disposed in said punch support an axially slidable thrust element for a piercing punch.

In a known piercing apparatus constructed as de-- scribed above, the piercing punch is non-rotatably engaged with the thrust element and is prevented from rotating relative to the punch support by the provision on the thrust element of a bar member having an arm provided with an inner guide plane surface which is adapted to slide along a flat wall of the punch support, while the punch support is prevented from rotating relative to the housing by virtue ofa further flat wall of the punch support arranged to slide along a flat lateral surface of a guide rail which is joined to the housing.

The said known piercing apparatus suffers from the disadvantage that in operation a certain amount of play soon arises between the guide plane of the arm of the bar member mounted on the thrust element and the flat wall of the punch support co-operating therewith, or between the other flat wall of the punch support and the guide rail co-operating therewith. Elimination of such play, which has a detrimental effect on the accuracy of piercing when non-circular holes are pierced, calls for exceptionally arduous, time-consuming and therefore costly work.

SUMMARY OF THE INVENTION An object of the invention is to construct a piercing apparatus in which the aforementioned disadvantage is eliminated in a simple but very effective manner.

The present invention provides piercing apparatus including a housing provided with a bore accommodating a punch support slidable axially in the bore, a thrust element slidable axially in the punch support, the punch support being adapted to receive an axially slidable piercing punch and the thrust element being arranged and adapted to be non-rotatably engaged with and to exert a piercing thrust on a .punch received in the punch support, and locating means respectively preventing rotation of the thrust element relative to the support and preventing rotation of the support relative to the housing, at least one said locating means comprising a resiliently-loaded guide element engaging an axially extending groove.

Reliable engagement between the parts whose relative rotation is to be prevented is ensured by the resilient loading of the guide elements even if a certain amount of wear of the guide element and the groove co-operating therewith occurs, so that the pierced holes remain accurate and clean even after a prolonged operating period.

The thrust element preferably comprises a sleeve having a cylindrical longitudinal bore, and a thrust pin fitted therein, the pin end nearer the punch having a non-circular recess for accommodating a non-circular punch head, which pin can be locked to the sleeve at any desired angle of rotation about its longitudinal axis.

In a particularly advantageous embodiment the punch support and/or the housing is provided with a tapped bore, extending at right angles to the piercing punch, a screw-threaded bush with a longitudinal bore having a constriction at the radially inner end being screw-mounted in the afore-mentioned tapped bore and the guide element being slidable in the said longitudinal bore under the thrust of a spring or other resilient means disposed therein so that the said guide element projects through the constriction.

When piercing very small holes and in particular if the thickness of the material to be pierced is greater than the diameter of the hole, there is a risk of the piercing punch bending during the piercing operation, so that it might break owing to fatigue effects. A further consequence of such bending of the piercing punch is that the accuracy of the piercing work is impaired.

It is of course possible for the greater part of the length of the piercing punch to be made thicker than the end which performs the actual piercing but such enlargement of the cross-section of the piercing punch is possible only to a limited extent, otherwise there is a risk of the piercing punch breaking in the zone of transition from the thick to the thin part.

In order to eliminate this risk in a simple but most effective manner, punch-guiding bush means are provided in the punch support, which means comprise a first bush portion adjacent to and arranged to move axially with the thrust element, and a second bush portion spaced from the thrust element and fast with the punch support, the bush portions having interengaged axially extending projections preventing relative rotation of the said portions, which projections have axial lengths exceeding the piercing stroke of the apparatus. The projections are preferably fingers, integrally formed on each bush portion and having a length which is greater than the length of stroke of the piercing punch. The bush portions and the projections thereof provide accurate guiding of the piercing punch in the punch support. The previously mentioned risks of bending and breakage of the punch are reliably eliminated since the piercing punch, or at least the part thereof which is not in contact with the workpiece to be pierced, is reliably guided in the guide bush means so that it cannot bend. The two-part construction of the guide bush means also enables holes to be pierced whose diameter is smaller than the thickness of the workpiece which is to be pierced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial longitudinal section through piercing apparatus embodying the invention.

FIG. 2 is a plan view of part of the piercing apparatus shown in FIG. 1.

FIG. 3 is a longitudinal section through a detail of the piercing apparatus to an enlarged scale.

FIG. 4 is an exploded view of the punch support of the apparatus, its internal parts being partially sec tioned.

DESCRIPTION OF A PREFERRED EMBODIMENT The piercing apparatus illustrated in the drawings is provided in particular for mounting on a crank press or the like and is specially designed for piercing noncircular holes. It comprises a substantially C-shaped housing 1, constructed of steel, the upper arm 1 having a vertical bore 2 formed therein in which the lower part of a punch support 3 is slidable. At its upper end the punch support 3 is provided with a thicker portion 4, a coil spring 5, which thrusts the punch support 3 towards an upper end position after each stamping operation, being located between the said portion 4 and the upper arm 1' of the housing 1.

A piercing punch 6, having a head 6', is disposed in the punch support 3. The piercing punch 6 has a close sliding fit in a guide bush 7, sub-divided into two bush parts 7 and 7" each having two fingers 8 with lateral surfaces which extend axially parallel to the piercing punch 6. The afore-mentioned two fingers 8 mesh accurately with each other and are longer than the length of stroke of the piercing punch so that their meshed engagement is maintained during the entire punching operation. The lower bush part 7' is mounted in the lower end of the punch support 3 and also functions as a stripper while the upper bush part 7" is provided at its upper end with an annular collar 9. A plurality of annular diaphragm springs 11 of conventional construction is disposed in a longitudinal bore 10 of the punch sup port 3, said annular springs surrounding the guide bush, the annular collar 9 of the upper bush part 7" bearing upon the uppermost of the annular springs. The head 6 of the piercing punch 6 bears on the top of the uppermost bush part 7". The diaphragm springs 11 rest on a lower internal shoulder of the longitudinal bore 10 and exert an upward stripping force on the piercing punch 6, through the upper bush part 7".

The head 6 of the piercing punch 6 is provided with two oppositely disposed flat surfaces by means of which it fits accurately into an indentation in the underside of a thrust pin 12' of a thrust element 12, which element bears on the top of the upper bush part 7" and is guided in the punch support 3. Rotation of the thrust element 12 relative to the piercing punch 6 is effectively prevented owing to the engagement of the noncircular head 6 of the piercing punch 6 in the correspondingly shaped indentation in the underside of the thrust pin 12'. As shown in detail in H6. 4, the thrust element 12 comprises a sleeve 12" having a cylindrical longitudinal bore in which the thrust pin 12 fits neatly. The sleeve 12" of the thrust element 12 is provided with a radially extending screw-threaded bore for accommodating a locking screw 13, while the thrust pin 12' is provided with a circumferential groove 14, corresponding to the afore-mentioned radial bore, so that the pointed end of the locking screw 13 maybe screwed into the said annular groove thus locking the sleeve relative to the thrust pin. Slackening of the locking screw 13 enables the thrust pin 12' to be rotated in the sleeve 12" so that the angular position of the piercing punch 6 may be accurately adjusted, a feature of particular importance for the piercing of non-circular holes. To factilitate rotation of the thrust pin 12' in the sleeve 12", the thrust pin 12' is provided with a head 16, projecting from the top of the sleeve 12" and having a knurled annular collar 15. The head part 16 extends above the collar to enable the punch of a crank press or the like to be placed thereon to exert the force required for piercing.

A vertical groove 17, parallel to the axis of punch 6 and having a V-shaped cross-section, is provided on the exterior of the sleeve 12" of the thrust member 12.

The lower end region of the punch support 3 is also provided with a vertically extending external groove 18 of V-shaped cross-section, parallel to the axis of punch 6.

Respective screw-threaded bores, extending at right angles to the piercing punch 6, are provided in the punch support 3 and in the housing 1, a guide element 19 being screw-threaded in each said bore. The guide element 19, shown on an enlarged scale in FIG. 3, comprises a screw-threaded mounting bush 20, having a removable cap 21, and a longitudinal bore 22 with a restriction 23 at the inner end, i.e., the end nearest the sleeve 12" or the support 3. A spring 24, which biases a guide pin 25, is disposed in the bore 22. A head 25 of the pin 25 can slide in the bore 22 and the shank 25" of the guide in projects through the restriction 23. The outer end of the longitudinal bore 22 is provided with internal screw-threading in which an adjusting screw 26 is screwed. The cap 21 is screwed onto the external threads of the bush 20 and can be removed for access to screw 26. The spring 24 is disposed between the head 25' of the guide pin 25 and the adjusting screw 26 so that the spring stress is adjustable by screwing of the adjusting screw. The tip of the shank 25" of the guide pin 25 is hemi-spherical so that it will engage reliably in the external groove 17 of the sleeve 12" or the external groove 18 of the punch support 3. Lock-nuts 27 are provided to permit reliable locking of the screwthreaded bushes 20 in their screw-threaded bores in the punch support or housing respectively. The construction described hereinabove ensures that the thrust ele ment 12 is able to reciprocate vertically in the punch support 3 and the said punch support is able to reciprocate vertically relative to the housing 1, but the thrust element 12 and therefore the piercing punch 6 cannot rotate relative to the punch support 3 which in turn cannot rotate relative to the housing 1.

Since the guide pins 25 are biased by the springs 24 and a certain amount of initial clearance is present between the head 25 and the constriction 23, the guide pin 25 will remain in reliable engagement with groove 17 or 18 even if, after some time of operation, wear takes place on the hemi-spherical tip of the shank 25" or in the groove. In order to avoid such wear as far as possible, the guide pins 25, the sleeve 12", and the punch support 3 may be constructed of hardened steel.

As an alternative to the embodiment described here inabove, balls may be employed instead of guide pins 25, said balls being also made of hardened steel and being slidably supported in the bore 22 of the bush 20.

The lower arm 1" of the housing 1 is provided with an aperture 28 into which a die bush 29 is fitted. The outside of the said aperture 28 is provided with a longitudinal slit 30, an Allen screw 31, extending transversely to said slit, being provided for the purpose of clamping the bush 29 in its aperture and enabling the bush to be exchanged if required. The bush 29 is provided with a central bore 29' coaxial with the piercing punch 6.

Furthermore, if the piercing punch 6, of non-circular cross-section, is rotated about its longitudinal axis in the manner already described relative to the punch support 3, the bush 29 can also be rotated through the same angle, after slackening of the screw 31, which is then re-tightened so that the bush 29 is once again clamped, in the desired position.

An opening 32 for the scrap is provided below the bush 29 in the lower arm 1" of the housing 1.

To enable the housing 1 to be mounted on a crank press or the like, the lower arm 1" has a slot 33 formed therein and a vertical centring pin, not shown in the drawing, may also be provided.

A horizontal stop bar 34, on which a stop abutment 35 can slide and can be locked in any desired position by means of two screws 36, is mounted in the housing 1, so that the workpiece may be located against the said stop abutment for the piercing operation.

As shown in the drawings, the greater part of the length of the piercing punch 6, which is thicker than its lower end portion which performs the piercing, has a close fit in and is guided in the guide bush 7 and is laterally supported thereby so that any bending of the piercing punch itself is prevented, even when piercing holes of a diameter which is smaller than the thickness of the material of the workpiece. Owing to the two-part construction of the guide bush 7 it is possible, without difficulty to pierce holes whose diameter is smaller than the thickness of the workpiece. It is even possible, to pierce very neatly holes whose diameter is only a fraction of the thickness of the workpiece.

The piercing of round holes is of course possible with a punch of circular cross-section.

What we claim is:

l. Piercing apparatus including a housing provided with a bore accommodating a punch support slidable axially in the bore, a thrust element slidable axially in the punch support, the punch support being adapted to receive an axially slidable piercing punch and the thrust element being arranged and adapted to be nonrotatably engaged with and to exert a piercing thrust on a punch received in the punch support, and locating means respectively preventing rotation of the thrust element relative to the support and preventing rotation of the support relative to the housing, at least one said locating means comprising a resiliently-loaded guide element engaging an axially extending groove.

2. Piercing apparatus as claimed in claim 1 wherein each said locating means comprises a spring-loaded guide element engaging an axially extending groove.

3. Piercing apparatus as claimed in claim 2 having said grooves in the external surface of the support and of the thrust element, the guide elements being mounted in the housing and in the support respectively.

4. Piercing apparatus as claimed in claim 3 in which each groove is a V-section groove.

5. Piercing apparatus as claimed in claim 4 in which the guide element has a spherical or part-spherical surface engaging the groove.

6. Piercing apparatus as claimed in claim 1 in which the guide element is axially movable in and projects from a longitudinal bore in a mounting bush whose axis is perpendicular to the punch axis, this bore being provided with a constriction retaining the guide element in the bore, and accommodating means resiliently loading the guide element in a direction such as to urge the guide element out of the bore.

7. Piercing apparatus as claimed in claim 6 in which the guide element is a pin having a head slidable in the longitudinal bore and a shank projecting from the bore.

8. Piercing apparatus as claimed in claim 7 in which the shank has a hemispherical tip.

9. Piercing apparatus as claimed in claim 6 in which the guide element is a ball.

10. Piercing apparatus as claimed in claim 6 in which the longitudinal bore has internal screw threading in which is threaded an adjusting screw acting on the resilient means, whereby the resilient loading exerted on the guide element can be adjusted.

ll. Piercing apparatus as claimed in claim 6 in which the mounting bush is screw-threaded in a lateral bore in the housing or punch support and is locked therein by a lock-nut.

l2. Piercing apparatus as claimed in claim 1 in which the thrust element comprises an outer sleeve slidable axially in and located non-rotatably relative to the punch support, and a thrust pin in the sleeve and adapted to be non-rotatably engaged with a piercing punch, the pin being rotatable in the sleeve and lockable at any selected rotational position in the sleeve.

13. Piercing apparatus as claimed in claim 12 in which the sleeve has a radial tapped bore accommodating a locking screw, and the thrust pin has a peripheral annular groove for engagement by the locking screw to lock the pin against rotation in the sleeve.

14. Piercing apparatus as claimed in claim 12 in which the thrust pin has a head projecting from the outer sleeve to receive a punch-operating force.

15. Piercing apparatus including a housing provided with a bore accommodating a punch support slidable axially in the bore, a thrust element slidable axially in the punch support, the punch support being adapted to receive an axially slidable piercing punch and the thrust element being arranged and adapted to be nonrotatably engaged with and to exert a piercing thrust on a punch received in the punch support, locating means respectively preventing rotation of the thrust element relative to the support and preventing rotation of the support relative to the housing, and punch-guiding bush means in the punch support, which means comprise a first bush portion adjacent to and arranged to move axially with the thrust element and a second bush portion spaced from the thrust element and fast with the punch support, the bush portions having interengaged axially extending projections preventing relative rotation of the said portions, which projections have axial lengths exceeding the piercing stroke of the apparatus.

l6. Piercing apparatus as claimed in claim 15 in which the projections are fingers with interengaging surfaces which are parallel to the punch axis. 

1. Piercing apparatus including a housing provided with a bore accommodating a punch support slidable axially in the bore, a thrust element slidable axially in the punch support, the punch support being adapted to receive an axially slidable piercing punch and the thrust element being arranged and adapted to be non-rotatably engaged with and to exert a piercing thrust on a punch received in the punch support, and locating means respectively preventing rotation of the thrust element relative to the support and preventing rotation of the support relative to the housing, at least one said locating means comprising a resiliently-loaded guide element engaging an axially extending groove.
 2. Piercing apparatus as claimed in claim 1 wherein each said locating means comprises a spring-loaded guide element engaging an axially extending groove.
 3. Piercing apparatus as claimed in claim 2 having said grooves in the external surface of the support and of the thrust element, the guide elements being mounted in the housing and in the support respectively.
 4. Piercing apparatus as claimed in claim 3 in which each groove is a V-section groove.
 5. Piercing apparatus as claimed in claim 4 in which the guide element has a spherical or part-spherical surface engaging the groove.
 6. Piercing apparatus as claimed in claim 1 in which the guide element is axially movable in and projects from a longitudinal bore in a mounting bush whose axis is perpendicular to the punch axis, this bore being provided with a constriction retaining the guide element in the bore, and accommodating means resiliently loading the guide element in a direction such as to urge the guide element out of the bore.
 7. Piercing apparatus as claimed in claim 6 in which the guide element is a pin having a head slidable in the longitudinal bore and a shank projecting from the bore.
 8. Piercing apparatus as claimed in claim 7 in which the shank has a hemispherical tip.
 9. Piercing apparatus as claimed in claim 6 in which the guide element is a ball.
 10. Piercing apparatus as claimed in claim 6 in which the longitudinal bore has internal screw threading in which is threaded an adjusting screw acting on the resilient means, whereby the resilient loading exerted on the guide element can be adjusted.
 11. Piercing apparatus as claimed in claim 6 in which the mounting bush is screw-threaded in a lateral bore in the housing or punch support and is locked therein by a lock-nut.
 12. Piercing apparatus as claimed in claim 1 in which the thrust element comprises an outer sleeve slidable axially in and located non-rotatably relative to the punch support, and a thrust pin in the sleeve and adapted to be non-rotatably engaged with a piercing punch, the pin being rotatable in the sleeve and lockable at any selected rotational position in the sleeve.
 13. Piercing apparatus as claimed in claim 12 in which the sleeve has a radial tapped bore accommodating a locking screw, and the thrust pin has a peripheral annular groove for engagement by the locking screw to lock the pin against rotation in the sleeve.
 14. Piercing apparatus as claimed in claim 12 in which the thrust pin has a head projecting from the outer sleeve to receive a punch-operating force.
 15. Piercing apparatus including a housing provided with a bore accommodating a punch support slidable axially in the bore, a thrust element slidable axially in the punch support, the punch support being adapted to receive an axially slidable piercing punch and the thrust element being arranged and adapted to be non-rotatably engaged with and to exert a piercing thrust on a punch received in the punch support, locating means respectively preventing rotation of the thrust element relative to the support and preventing rotation of the support relative to the housing, and punch-guiding bush means in the punch support, which means comprise a first bush portion adjacent to and arranged to move aXially with the thrust element and a second bush portion spaced from the thrust element and fast with the punch support, the bush portions having interengaged axially extending projections preventing relative rotation of the said portions, which projections have axial lengths exceeding the piercing stroke of the apparatus.
 16. Piercing apparatus as claimed in claim 15 in which the projections are fingers with interengaging surfaces which are parallel to the punch axis. 